As was already said it's all one pond, just multiple pools. So total volume.
However, beware of 100,150,200,500% numbers. Just because something is repeated a million times on the web doesn't actually make it valid. These are just pulled out of thin air and have no basis whatsoever in reality.
In San Jose CA I ran a 5000 gal multi-pool pond with a 900 GPH pump. So that's 18% turn over per hour. Go into any pond forum and say that and you will get an ear full. But I ran that pond for many years without a problem. That doesn't mean I think 18% is some kind of minimum...there were times when that pump was off for weeks and the fish were fine. Had a gunite swimming pool I kept goldfish in for several years. 35,000 gal and no pump at all and that pond had a ton (I think literally) of the nastiest muck I've ever seen (and I cleaned ponds for a time). Fish were fine.
On the other hand I've had small ponds where I was raising a bunch of fry and I needed 1000% turn over. If the pump was off for more than 20-30 minutes I could lose all the fish. Doesn't mean every pond needs 1000% turn over.
Unless you have some specific goal, like you want to grow monster big Koi, or a huge amount of fish, the chances are no pump is needed. Yeah, there can be certain periods, like algae die offs, when gas exchange (what you call aeration) is important. But you're right back in the same boat, how much is enough? A static percentage just makes no sense other than to lure you into a false sense of security.
I think for most normal type backyard water gardens you're way better off sizing the pump to your budget and water features you want (sound, looks). As far as water quality goes the pump size is way down the list. Other things will have a much larger impact.
Next myth...waterfalls provide great gas exchange (aeration). We see that white water, the bubbles, and think it's the poster child of goodness. The truth is gas exchange happens at the surface of water so virtually all of it happens at that flat calm surface across the entire pond. Water can only hold so much O2 so yeah the water in the falls is maxed out, but so is the top 1" of the entire pond. Plus most of the falls water stays near the surface so no great gas exchange benefit since that water is already maxed out.
As you go deeper the O2 level drops. So if you want improved gas exchange the trick is to move that deeper water up to the surface where gas exchange can happen. If you used the same amount of flow going to the falls to instead use it rotate the entire pond you would get many times better gas exchange (and O2 levels) in the entire pond. So this myth about waterfalls really hurts a lot of ponds. Yet it persists.
You can have your cake and eat it too. The main problem with waterfalls and gas exchange is the water plunging into the pond doesn't penetrate very well. It hits the surface and basically spreads out. Most of the flow doesn't mix the bottom water very well. That can be easily changed. You can add a catch basin under the falls to make sure all water goes to the bottom and rotates the entire pond. Win - win. Easy and cheap to build too.
Looks like this when done:
You can do the exact same thing again in the lower pond where the stream enters that pool. For the cost of pumping water once you get a pretty waterfall
and good gas change in 2 pools, or as many pools as you like.
The basin has other benefits like never having soap foam on the surface of your pond, better fish viewing, extra bio filtering, and other good stuff.
That type of water movement might give you 10 times better exchange than just a falls. That's why these % rules make no sense. The design of the pond, fish load, and other factors matter way more. Made up numbers that only sound good, matter not so much.
